T he development of irreversible dilations of the infrarenal aorta has been attributed to hemodynamic disturbances as well as to structural and metabolic changes within the vessel wall. 1 -2 Chemical and histological analyses have demonstrated significant decreases in the two major structural proteins, collagen and elastin, in dilated vascular tissue from patients undergoing corrective surgery for abdominal aortic aneurysm (AAA) disease. 34 Experimentally, it has been shown that circumferential arterial wall stress is borne primarily by elastin and that collagen maintains the integrity of the arterial wall, as enzymatic hydrolysis of collagen results in vessel rupture, whereas degradation of